Mr O'Mara suffers from cerebral palsy and autism, and says he's been so depressed he tried to kill himself three times while he was suspended.

In an open letter, the MP said: "It is with great sadness that today I have decided to announce my departure from the Labour party with immediate effect.

"This decision has not been taken lightly but has been made following careful reflection of the decision to re-admit me back into the Labour party following my suspension last October.

"I feel I have not been listened to or been given a fair investigation as I do not believe they considered my supporting evidence or got in touch with my witnesses.

"Furthermore, I am of the opinion that the Labour party no longer shares my commitment to the true definition of equality and compassion."

He added: "I didn’t commit any crimes, yet I have been made unfairly to feel like a criminal. Nobody should be made to feel ashamed for mistakes they make when they are young.

"I would be lying to those of you whom I represent, and those close to me like my parents and sister respectively, if I continued under the pretence that I feel there is a place of acceptance and empathy for me as a working class, underprivileged disabled man within the Labour party.

"I have experienced little to make me feel welcome, understood and accepted during this last year."

Mr O'Mara insisted he would continue serving as an independent MP and vowed to stand up for his constituents in Parliament.

Labour tonight insisted they did handle his case properly and changed the normal procedures to take account of his disabilities.

A source told The Sun: "The party handled this investigation with care and sensitivity and has treated Jared’s welfare as a priority throughout."

Last week the party announced Mr O'Mara would be given a formal warning and told to attend sensitivity training.

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A Labour spokesman said: "We're disappointed Jared has decided to resign from Labour after we won the Sheffield Hallam seat from Nick Clegg and the Lib Dems last year. We wish him well for the future."

Mr O'Mara defeated Sir Nick, who had held the seat for 12 years, by a margin of 2,125 votes at last year's snap election.

The Lib Dems have called for him to quit the Commons and are adamant they will win the seat back if there is a by-election.

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